1. Field of the Invention
The invention disclosed broadly relates to the field of enclosures and chassis for electronics and other devices, and more particularly relates to the field of cover fabrication, especially sheet metal plate cover fabrication.
2. Description of the Related Art
Although the use of plastic enclosures has been increasing over the last few years, sheet metal enclosures are still used for certain applications. One application is in the area of enclosures for electronics and speciality Personal Computers PCs. The use of metal has many desirable characteristics over plastic. One desirable characteristic is the relatively lower expense to set up fixturing and/or tooling for a limited product chassis and enclosures. Another desirable characteristic is the ability to reduce the emissions of electro-magnetic-waves emanating from the enclosed electronic circuitry. Still, another desirable characteristic is the durability of sheet metal in many applications such as in industrial environments over plastics. Yet still another desirable characteristic is flame and fire retardant such as meeting the UL (Underwriters Laboratory) 5 V specification.
One speciality product in which sheet metal enclosures have been used is a wall hanging PC. The wall hanging PC as the name suggests provides a PC chassis or system unit that can hang on the wall rather than taking up desk space or floor space. The Canadian Standards Association (CSA) specification 22.2 No. 950 Manual Section 4.4.6 and UL 1950 for wall mounted PCS states that the maximum opening on the bottom of the unit cannot be greater than two millimeters (2 mm) in diameter. Many times the requirements for cooling devices such as fans, and the requirements for cabling and connecting to other equipment makes this maximum opening specification difficult to meet. To meet this requirement often suppliers of chassis for wall mounted PCs use covers and grommets to fill or cover holes larger than the 2 mm. maximum opening. One cover that is difficult and expensive to make is the cover for a fan opening on a PC power supply. This cover can typically be 50 millimeters or more in diameter. The cover must be fastened securely in place so that it will not rattle or be dislodged thereby violating the CSA and UL specification. Many manufactures attach covers by use of spot welds or by the use of mechanical fasteners such as screws or rivets. This method of fastening although effective in minimizing the possibility of dislodging a cover, is expensive. Manufactures must build jigs for welding and add a step of spot welding during the assembly of the sheet metal chassis. If screws or other mechanical fasteners are used, the steps of drilling holes, aligning holes and securely mounting fasteners must be performed. Each of these additional steps or processes during the manufacturing of a metal chassis adds cost to the final product. Accordingly, a need exists to provide a method and apparatus to reduce cost of mounting covers on stamped or formed openings.
The need to cover openings that may protrude from a chassis or that may be recessed in a chassis is often required. Many PC components such as the power supply have protrusions from it for the fans and other components such as removable pluggable units and subassemblies. Covers for these protruding or recessed openings are often welded in the case of metal, glued in the case of non-metals such as plastics or fastened in place using mechanical fasteners. The need to fabricate covers having different offsets or depths with respect to a chassis or enclosure is required. Therefore, a need exists to provide a cost effective method and apparatus to provide cover assemblies of a variety of depths.